In the discussion of the background that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art.
A cemented carbide cutting tip for soft cutting conditions generally has a flat rearward facing bonding surface for joining the cutting tip to the head of a tool pick to form a cutting bit. In tougher conditions, a cutting tip that utilizes a recessed or “valve seat” bonding surface is preferred because it can generally withstand higher shear stresses than a cutting tip having a “flat-bottom” bonding surface without becoming dislodged from the tool pick head. Regardless, whether of the flat bottom design or the valve seat design, conventional tips for cutting bits suffer from using an excess of cemented carbide material and from difficulties during assembly.
Additionally, cutting tips of the valve seat design require more material than those of the flat bottom design, since the valve seat is formed by a solid projection of the material of the cutting tip that is countersunk into the body of the tool pick. Thus, while the valve seat design increases the bonding strength of the cutting tip to the tool pick head, it significantly increases the volume of hard material required. The carbide in the valve seat does not contribute to the cutting performance of the cutting bit because the valve seat is used for bonding and the cutting bit loses effectiveness well before the valve seat is exposed by wear processes.
In contrast, a flat bottom cutting tip avoids the need for excess material to form a valve seat. However, because the flat bottom provides less resistance to shear stresses encountered during cutting, a flat bottom cutting tip may be more prone to detachment from the tool pick head during severe cutting conditions. Additionally, alignment during assembly and bonding can be an issue with conventional flat bottom tip designs because flat bottom tips are difficult to keep centered. When cutting tips are “misaligned,” operators may be required to correct their orientation, which can be hazardous particularly during hot brazing processes.